The accident on Monday left the Boeing 737-700 with its nose resting against the runway and forced the temporary closure of the airport, which mostly handles flights to and from other US cities.

The airline confirmed that emergency services had helped with the evacuation of the passengers and crew of flight 345 from Nashville. "Eyewitness reports indicate the aircraft's nose gear collapsed upon landing," it said in a statement.

"Initial reports indicate local responders are caring for five customers and three flight attendants who have reported injuries at this time. Southwest is cooperating with local authorities, and the (US aviation safety body) NTSB has been notified."

Television images showed the plane with its nose angled down to the ground and its evacuation slides out. The fuselage was surrounded by emergency vehicles. Passengers on board the plane saw sparks flying as the nose scraped along the runway, according to accounts given to waiting relatives and friends.

Planes scheduled to fly to La Guardia were held at their origin airports, while those already en route were diverted to New York's other hubs, Newark and John F Kennedy, contributing to long delays. All take-offs were suspended for more than two hours after the incident.

The NTSB said it would be sending an investigator to La Guardia to look into the incident. Three people were killed and 180 were injured earlier this month when an Asiana Airlines Boeing 777 crashed while landing in San Francisco.

According to preliminary findings from the NTSB, the Asiana flight crashed because it was flying too low and too slowly as it approached the runway.

The tail of the aircraft broke off as the plane clipped a seawall short of the runway, skidding out of control and quickly catching fire.